This application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2005-274221 filed in Japan on Sep. 21, 2005, the entire contents of which are hereby incorporated by reference.
The present invention relates to original feeding devices that are provided in copying machines, fax machines or the like that perform capturing to copy or transmit an original, and draw an original out of an original tray to forward the same.
In devices of this type, when an original P is placed on an original tray 101 as illustrated in FIGS. 16 and 17, a drawing roller 102 is caused to contact the proximity of the leading edge of the original P, and is rotated so as to draw the original P for forwarding the same. The original P is transported to PS rollers 104 via separating rollers 103 for separating originals one by one, and is transported through the PS rollers 104 to a scanner (not shown). The scanner captures an image of the original.
As illustrated by the dashed line in FIG. 17, when the original P drawn by the drawing roller 102 is transported at a slant to the scanner and captured, the image of the original P is captured at a slant. Therefore, the leading edge of the original P is abutted against the PS rollers 104 for alignment, before being transported to the scanner.
However, in a case where the original P is slanted significantly when the original P is drawn by the drawing roller 102, it becomes impossible to align the leading edge of the original P parallel to the PS rollers 104 merely by abutting the original P against the PS rollers 104.
Even if the leading edge of the original P could be aligned parallel to the PS rollers 104 by being abutted against the PS rollers 104, the direction of the original P has been changed and a center line p1 of the original P is displaced from a capturing center s1 of the original by the scanner, as shown in FIG. 18. Even a slight amount of such displacement makes it impossible for the scanner to capture the edge portions of the original. Therefore, an original with no margin at the edges cannot be captured accurately.
For this reason, a pair of guide plates 105 for guiding the original are provided in the original tray 101 so as to prevent slanted transport of the original. In addition, each guide plate 105 is arranged in a manner that the pair of guide 105 plates can be shifted symmetrically with respect to the capturing center of the original. The distance between the guide plates 105 is adjusted according to the width of the original so as to guide originals with various widths with the guide plates 105 without displacing the capturing center of the original.
JP H11-79435A (hereinafter referred to as “Patent Document 1”) discloses technology in which a pair of ancillary rollers are provided at both ends of the drawing roller (referred to as the “forwarding roller” in the Patent Document 1) on the side further upstream in the original forwarding direction than the drawing roller, and causes the ancillary rollers to press the original together with the drawing roller in order to prevent slanted transport of the original.
JP H8-282880A (hereinafter referred to as “Patent Document 2”) discloses technology in which a pressure roller is arranged on the side further upstream in the original forwarding direction than the drawing roller (referred to as the “transport roller” in the Patent Document 2), and causes the pressure roller to press the original together with the drawing roller in order to prevent slanted transport of the original.
However, even if a pair of guide plates 105 are provided as illustrated in FIG. 17, in a case where the widths of a plurality of sheets of originals placed between the guide plates 105 are different from one another, only the original with the greatest width is guided by the guide plates 105, and other originals with smaller widths are not guided by the guide plates 105. Consequently, the originals with smaller widths are transported at a slant.
Generally, originals of the same size are transported for capturing, and therefore, all originals are appropriately guided by the guide plates 105. However, a use condition is also possible in which a plurality of originals with different widths are captured in a mixed state. In such a case, even if these originals are placed on the original tray, not all the originals are guided by the guide plates 105, and the originals with smaller widths are transported at a slant, resulting in defective capturing.
In addition, when ancillary rollers are provided as in Patent Document 1 and Patent Document 2, the mechanism itself becomes complicated, often inviting an increase in size, and also the mechanism for interlocking ancillary rollers with the drawing roller increases in size.
Furthermore, in the method of pressing the ancillary rollers against the original as described in Patent Document 1, a plurality of locations on the original are pressed by the drawing roller and the ancillary rollers to prevent slanted transport of the original. However, even if the original is pressed by the rollers, the direction of the original easily changes during rotation of the rollers. As a result, sufficient braking force for resisting the rotation moment of the original cannot be generated, and therefore substantial effects cannot be expected. Increasing the pressure of the ancillary rollers against the original to improve the braking force makes transport of the original itself difficult. Adjustment of the pressure of the ancillary rollers is difficult even with these measures. Consequently, adequate effects cannot be achieved.
As described above, with the conventional technology, it has been impossible to concurrently achieve both generating sufficient braking force that resists the rotation moment of the original and smooth transport of the original.